背景及目的
由于各个开发者使用的开发语言可能在官方SDK找不到相应的语言版本，就必须自主开发SDK。
本文根据wireshark和API文档，来简单实现上传和下载的请求，给需要自主开发的开发者提供一个简单的示例。
准备工作
安装wireshark
官网地址：https://www.wireshark.org/download.html
找到合适的平台及版本，下载并安装。
找到OSS的API文档
官网地址：https://help.aliyun.com/document_detail/oss/api-reference/abstract.html
准备开发环境
1. 这里使用的是python 2.7, 并且使用requests库。
http://cn.python-requests.org/zh_CN/latest/
2. 需要开通OSS，并且拥有一个bucket，同时需要获取AccessKeyId和AccessKeySecret
实践
基于OSS API文档，用python实现一个简单的上传和下载操作
上传
1. 先看Put Object的API文档
https://help.aliyun.com/document_detail/oss/api-reference/object/PutObject.html
请求语法
PUT /ObjectName HTTP/1.1
Content-Length：ContentLength
Content-Type: ContentType
Host: BucketName.oss-cn-hangzhou.aliyuncs.com
Date: GMT Date
Authorization: SignatureValue2. 构建类似的HTTP请求
BucketName是ali-beijing
Endpoint是oss-cn-beijing.aliyuncs.com
ObjectName是test.txt
将如下的代码保持文件后运行
import requests
bucket = "ali-beijing"
objectname = "test.txt"
endpoint = "oss-cn-beijing.aliyuncs.com"
url = "http://%s.%s/%s" % (bucket, endpoint, objectname)
headers = {}
r = requests.put(url, data="hello", headers=headers)
print r.text
print r.status_code
print r.headers3. 运行的同时，打开wireshark来抓包，查看请求
运行完毕后，停止抓包，查看请求。
如图所示：
停止抓包后点击图中红框的"Protocol"，找到发送的HTTP请求，然后点击“Analyze"->"Follow TCP Stream"，即可看到整个HTTP请求的内容。
可以看到最终的HTTP请求如下所示
PUT /test.txt HTTP/1.1
Host: ali-beijing.oss-cn-beijing.aliyuncs.com
Content-Length: 5
User-Agent: python-requests/2.5.1 CPython/2.7.10 Darwin/15.0.0
Connection: keep-alive
Accept: */*
Accept-Encoding: gzip, deflate
hello
HTTP/1.1 403 Forbidden
Server: AliyunOSS
Date: Tue, 26 Apr 2016 10:01:20 GMT
Content-Type: application/xml
Content-Length: 279
Connection: keep-alive
x-oss-request-id: 571F3C704FF4F07A6A0080A6
<?xml version="1.0" encoding="UTF-8"?>
<Error>
<Code>AccessDenied</Code>
<Message>You have no right to access this object because of bucket acl.</Message>
<RequestId>571F3C704FF4F07A6A0080A6</RequestId>
<HostId>ali-beijing.oss-cn-beijing.aliyuncs.com</HostId>
</Error>
经过和Put Object的协议对比，我们可以看到，请求的header中没有加入Authorization，以及Date，也没有Content-Type。由于bucket是私有权限，没有Authorization的认证信息是无法对bucket进行写入操作。所以需要加入签名信息。
4. 根据API文档描述的，加入签名的信息
签名相关的文档见：
https://help.aliyun.com/document_detail/oss/api-reference/access-control/signature-header.html
#coding=utf-8
import requests, datetime, hmac, httplib, hashlib
from email.utils import formatdate
from urllib import quote
from base64 import b64encode
class OssRequest():
def __init__(self, endpoint, AccessKeyId, AccessKeySecret, bucket):
self.endpoint = endpoint
self.AccessKeyId = AccessKeyId
self.AccessKeySecret = AccessKeySecret
self.bucket = bucket
self.objectname = ""
self.subresource = ""
self.VERB = ""
def format_oss_headers(self, headers=None):
map = {}
for header, value in headers.iteritems():
header = header.lower()
if header.startswith("x-oss-"):
map.setdefault(header, []).append(value)
parts = []
for key in sorted(map):
parts.append("%s:%s\n" % (key, ",".join(map[key])))
return "".join(parts)
def canonical_resource(self):
resource = "/"
if self.bucket:
resource += self.bucket + "/"
if self.objectname:
resource += "%s" % self.objectname
if self.subresource:
resource += "?%s" % quote(self.subresource, "/")
return resource
def sign(self, headers=None):
if not headers:
headers = {}
AuthString = "\n".join(str(item_) for item_ in items) + "\n"
CanonicalizedOSSHeaders = self.format_oss_headers(headers)
CanonicalizedResource = self.canonical_resource()
AuthString = "".join((AuthString, CanonicalizedOSSHeaders, CanonicalizedResource))
Signature = '%s' % (b64encode(hmac.new(AccessKeySecret, AuthString.encode("utf-8"), hashlib.sha1).digest()))
return Signature
def put(self, objectname):
self.VERB = 'PUT'
self.objectname = objectname
url = "http://%s.%s/%s" % (self.bucket, self.endpoint, self.objectname)
headers = {'Date' : formatdate(None, usegmt=True)}
Signature = self.sign(headers)
headers['Authorization'] = 'OSS %s:%s' % (self.AccessKeyId, Signature)
r = requests.put(url, data = "hello", headers=headers)
print r.text
print r.status_code
print r.headers
if __name__ == "__main__":
AccessKeyId = "替换成自己的AccessKeyId"
AccessKeySecret = "替换成自己的AccessKeySecret"
bucket = "ali-beijing"
objectname = "test.txt"
endpoint = "oss-cn-beijing.aliyuncs.com"
a = OssRequest(endpoint, AccessKeyId, AccessKeySecret, bucket)
a.put(objectname)5. 再次在运行后，通过wireshark抓包观察
同之前的抓包和观察方法，可以看到，上传成功了。
PUT /test.txt HTTP/1.1
Host: ali-beijing.oss-cn-beijing.aliyuncs.com
Content-Length: 5
Accept-Encoding: gzip, deflate
Accept: */*
User-Agent: python-requests/2.5.1 CPython/2.7.10 Darwin/15.0.0
Connection: keep-alive
Date: Tue, 26 Apr 2016 13:44:42 GMT
Content-Type: plain/text
Authorization: OSS testaliyun:1aUnxjJ4V/0+pTwzd7t9An3d10c=
helloHTTP/1.1 200 OK
Server: AliyunOSS
Date: Tue, 26 Apr 2016 13:44:42 GMT
Content-Length: 0
Connection: keep-alive
x-oss-request-id: 571F70CA4FF4F07A6A022212
ETag: "5D41402ABC4B2A76B9719D911017C592"
x-oss-hash-crc64ecma: 11177612005948864433下载
1. 查看Get Object的API文档
https://help.aliyun.com/document_detail/oss/api-reference/object/GetObject.html
GET /ObjectName HTTP/1.1
Host: BucketName.oss-cn-hangzhou.aliyuncs.com
Date: GMT Date
Authorization: SignatureValue
Range: bytes=ByteRange(可选)2. 在上传成功的基础上实现下载
由于之前上传Object已经成功，这里只需要添加如下代码
省略和上传一样的代码
在def put(self, objectname):
函数下添加
def get(self, objectname):
self.VERB = 'GET'
self.objectname = objectname
url = "http://%s.%s/%s" % (self.bucket, self.endpoint, self.objectname)
headers = {'Date' : formatdate(None, usegmt=True)}
Signature = self.sign(headers)
headers['Authorization'] = 'OSS %s:%s' % (self.AccessKeyId, Signature)
r = requests.get(url, headers=headers)
print r.text
print r.status_code
print r.headers
调用的时候在a.put(objectname)下添加a.get(objectname)3. 抓包观察
GET /test.txt HTTP/1.1
Host: ali-beijing.oss-cn-beijing.aliyuncs.com
Accept-Encoding: gzip, deflate
Accept: */*
User-Agent: python-requests/2.5.1 CPython/2.7.10 Darwin/15.0.0
Connection: keep-alive
Date: Tue, 26 Apr 2016 14:16:32 GMT
Authorization: OSS testaliyun:ARRfi3zGoiGdrAjmM5lJ0o4LEBA=
HTTP/1.1 200 OK
Server: AliyunOSS
Date: Tue, 26 Apr 2016 14:16:32 GMT
Content-Type: plain/text
Content-Length: 5
Connection: keep-alive
x-oss-request-id: 571F78404FF4F07A6A023023
Accept-Ranges: bytes
ETag: "5D41402ABC4B2A76B9719D911017C592"
Last-Modified: Tue, 26 Apr 2016 13:44:42 GMT
x-oss-object-type: Normal
x-oss-hash-crc64ecma: 11177612005948864433
Cache-Control: max-age=86400
hello以上是根据API文档，简单实现的上传和下载操作。
代码都是很简单的，没有异常的重试，也没有考虑大文件的上传和下载。
主要目的是演示如何通过wireshark和API文档来构建HTTP 请求来实现OSS的相关接口。
常见问题
1. Content-MD5计算错误
以消息内容为"123456789"来说，计算这个字符串的Content-MD5
正确的计算方式：
标准中定义的算法简单点说就是：
1. 先计算MD5加密的二进制数组（128位）。
2. 再对这个二进制进行base64编码（而不是对32位字符串编码）。
以Python为例子：
正确计算的代码为：
>>> import base64,hashlib
>>> hash = hashlib.md5()
>>> hash.update("0123456789")
>>> base64.b64encode(hash.digest())
'eB5eJF1ptWaXm4bijSPyxw=='
需要注意
正确的是：hash.digest()，计算出进制数组（128位）
>>> hash.digest()
'x\x1e^$]i\xb5f\x97\x9b\x86\xe2\x8d#\xf2\xc7'
常见错误是直接对计算出的32位字符串编码进行base64编码。
例如，错误的是：hash.hexdigest()，计算得到可见的32位字符串编码
>>> hash.hexdigest()
'781e5e245d69b566979b86e28d23f2c7'
错误的MD5值进行base64编码后的结果：
>>> base64.b64encode(hash.hexdigest())
'NzgxZTVlMjQ1ZDY5YjU2Njk3OWI4NmUyOGQyM2YyYzc='2. 某些头部没有加入到签名的计算中
例如x-oss-开头的header没有加入到签名的计算中。
3. Content-Type设置不对
上传Objec的时候没有设置正确的Content-Type，导致浏览器等无法根据Content-Type进行预览等处理。
